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An astronaut on the moon wishes to calculate the local g in the area. He sets up a wire with a mass of 1.7 grams and hanging from it an object with mass 4.98 kg. He sends some kind of pulse down the wire and calculates that it takes 40.86 ms to traverse the wire. What is g? You can neglect the mass of the wire when calculating the tension.
That was everything that was given in the problem. I have not a clue how to solve it. What I did was just use the equation of T=2pi[sqrt(l/g)] to solve for g and hope that the wire acts like a spring or something.
I’m totally sure that’s incorrect, but hey I’m not an astrophysicist.
(Response from Members and visitors awaited)
Posted by Ashish Dharva
- Change in resistance of a wire on stretching (askphysics.com)
A WIRE OF LENGTH L AND AREA OF CROSS SECTION A HAS A RESISTANCE R. IF THE WIRE IS STRACHED TO TWICE OF ITS LENGTH WHILE A REMAINS SAME , WHAT IS THE NEW RESISTANCE????
We know that R = ρl/A
When the wire is stretched, there is no change in volume. So if length is doubled then volume will be halved so that volume is constant.
Therefore, the new resistance R’ = 4R
That is the resistance becomes four times its original value.
1. A WIRE OF LENGTH L AND AREA OF CROSS SECTION A HAS A RESISTANCE R. IF THE WIRE IS STRACHED TO TWICE OF ITS LENGTH WHILE A REMAINS SAME , WHAT IS THE NEW RESISTANCE????
Why we specifically note resistance in a circuit while all part of a wire have some resistance..???
The resistance of the rest of the circuit compared to the resistance of the resistor is negligible.
Is it true that a person touching a high power line get struck with the line?
Ya, This is due to the strong contraction of the muscles making the person not at all able to release the wire or object from which he got the shock. Not due to any type of attraction arising out of electricity.
I am using 18 gauge nicrome wire having ohm of 17.3 , 220 volt. I want to use 10 gauge wire how to decide the length?
18 gauge corresponds to a diameter of 1.22 mm
Therefore radius r1= 1.22/2=0.61 mm=0.00061m
10 gauge means diameter is 3.25 mm
Radius r2 = 3.25/2=1.625mm=0.001625m
Sine the resistance needs to be the same, we can use the formula
As resistivity is same.
Substitute the values and you will get the answer.
If you are preparing for the CBSE Summative Assessment I for Class X, Give the following questions a try.
If you are not able to solve any of it, please post your doubts as comments to this post. The questions can be discussed here with due explanations.
Make it a practice to solve as much Sample papers and Guess papers as you can before writing the Board Exam.
All the best
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